Magnetic drive pump

ABSTRACT

A magnetic drive pump includes a pump chamber, a partition wall separating the pump chamber from an exterior portion, an impeller disposed in the pump chamber and rotating around a rotation axis, an inductor unitarily rotating with the impeller around the rotation axis, a magnet unit disposed at a position of the exterior portion separated by the partition wall where the magnet unit faces the inductor in a radial direction of the rotation axis, the magnet unit being rotatable around the rotation axis, and a rotation driving means driving the magnet unit to rotate, wherein a displacement mechanism is provided for changing a radial distance between the magnet unit and the inductor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C §119 with respect to Japanese Patent Application 2007-269224, filed on Oct. 16, 2007, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a magnetic drive pump transmitting rotative power to an impeller by exploiting magnetic force, and in particular relates to a pump which is suitably used as a water pump of an engine.

BACKGROUND

A water pump for an engine is disclosed as a known magnetic drive pump in paragraph 0004 to 0014 of JP 2005-139917A. The water pump is provided with an impeller, rotatably held inside a pump chamber and rotating to generate fluid flow in the pump chamber, and a driving mechanism driving the impeller to rotate. The driving mechanism is comprised of magnets and inductors. Each magnet is integrally fixed to a driving member which is rotatably positioned at an exterior portion from a partition wall separating the pump chamber from the exterior portion. Each inductor is integrally fixed to the impeller and is powered by induced current generated with rotation of the magnets. When the engine rotates at a high speed, rotation difference occurs between the magnet and the inductor. Consequently, a non-linear relationship is observed between the engine rotation number and the impeller rotation number. Namely, the increase rate of the impeller rotation number is lowered against the engine rotation number. Thus, when the engine rotates at a high speed, excessive rotation of the impeller is avoided, and unnecessary work is prevented in pumping. On the other hand, when the engine rotates at a low or a medium speed, a linear relationship is observed between the engine rotation number and the impeller rotation number, and the impeller rotation number is in proportion to the engine rotation number. Even in the case, the coolant is circulated more than necessary in certain circumstances. For example, even when the engine rotates at a medium speed, even when the engine is cold, or even when the engine is driven in a range that the coolant is not required to circulate at a high rate, such as low load steady operation, the coolant is circulated more than necessary. As a result, engine warm-up efficiency deteriorates, and fuel efficiency decreases due to unnecessary work.

A need exists for a magnetic drive pump which is not susceptible to the drawback mentioned above.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a magnetic drive pump includes a pump chamber, a partition wall separating the pump chamber from an exterior portion, an impeller disposed in the pump chamber and rotating around a rotation axis, an inductor unitarily rotating with the impeller around the rotation axis, a magnet unit disposed at a position of the exterior portion separated by the partition wall where the magnet unit faces the inductor in a radial direction of the rotation axis, the magnet unit being rotatable around the rotation axis, and a rotation driving means driving the magnet unit to rotate, wherein a displacement mechanism is provided for changing a radial distance between the magnet unit and the inductor.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:

FIG. 1 is a sectional view of a magnetic drive pump according to a first embodiment of the invention, in which a magnet unit and an inductor are positioned close to each other;

FIG. 2 is a sectional view of the magnetic drive pump according to the first embodiment of the invention in which the magnet unit and the inductor are spaced away from each other;

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is an exploded perspective view showing a magnet unit, a magnet unit holder, and a displacement mechanism in the magnetic drive pump according to the first embodiment of the invention;

FIG. 6 is a sectional view of a magnetic drive pump according to a second embodiment of the invention, in which a magnet unit and an inductor are positioned close to each other;

FIG. 7 is a sectional view of a magnetic drive pump according to the second embodiment of the invention, in which the magnet unit and the inductor are spaced away from each other;

FIG. 8 is a sectional view taken along line VIII-VIII of FIG. 6;

FIG. 9 is a sectional view taken along line IX-IX of FIG. 7; and

FIG. 10 is an exploded perspective view showing the magnet unit, a magnet unit holder, and a displacement mechanism in the magnetic drive pump according to the second embodiment of the invention.

DETAILED DESCRIPTION

FIGS. 1 to 5 show a first embodiment in which a magnetic drive pump is employed as a water pump 100 of an engine. The water pump 100 is fixed to an engine block 1 by a fastening tool (not shown).

The water pump 100 is provided with a housing 12. The housing 12 is disposed in a manner to cover a recessed portion 1 a formed at the engine block 1, and defines a pump space. The pump space is divided into a pump chamber 10 and an exterior chamber 11 (exterior portion) by a partition wall 13 made of a non-magnetic material. The pump chamber 10 is positioned at a side of the engine block 1, and the exterior chamber 11 is positioned at the exterior portion of the pump chamber 10.

An impeller 20 is disposed so as to rotate around a rotation axis X inside the pump chamber 10. The impeller 20 is supported by a supporting shaft 22 via a bearing 21 which is coaxially arranged with the rotation axis X. One end of the supporting shaft 22 is fitted into a cup shaped recessed portion 13 a formed at a center of the partition wall 13. Thus, the supporting shaft 22 is supported by the partition wall 13 at one side thereof. The impeller 20 rotates in the pump chamber 10 to generate flow of coolant in the pump chamber 10.

The impeller 20 is provided with a sleeve portion 20 a at a rear surface thereof to fit with the bearing 21. A cylindrical inductor 30 is comprised of an iron core 31 and a conductive portion (pure aluminum portion) 32. The iron core 31 is fixed to an outer circumferential surface of the sleeve portion 20 a, and the conductive portion 32 is disposed at the iron core 31. The inductor 30 and the impeller 20 unitarily rotate around the rotation axis X.

In a radial outward direction of the inductor 30, magnet units 40 are disposed at an opposite side of the partition wall 13, i.e. the exterior chamber 11, so as to rotate around the rotation axis X. Further, in an axial outward direction of the inductor 30, a magnet unit holder 50 is disposed at the opposite side of the exterior chamber 11, i.e. the exterior chamber 11, so as to rotate around the rotation axis X. The six magnet units 40 are uniformly spaced around the rotation axis X, and each magnet unit 40 is held by the magnet unit holder 50.

Each magnet unit 40 is comprised of a permanent magnet 41 and a yoke 42 to which an upper surface of the permanent magnet 41 is attached. The permanent magnet 41 corresponds to a segment formed by dividing a cylindrical magnet into a six equal parts in the circumferential direction. The cylindrical magnet has a diameter which is slightly larger than an outer circumferential surface of the inductor 30. As is apparent from FIG. 5, the yoke 42 is comprised of a magnet attaching portion 42 a having an attachment surface, to which the permanent magnet 41 is attached, an arm portion 42 b, and a leg portion 42 c. The arm portion 42 b extends in an axial direction of the rotation axis X from the magnet attaching portion 42 a, and the leg portion 42 c extends in a direction toward the axis from a distal end of the arm portion 42 b. Each permanent magnet 41 is disposed so that the north pole and the south pole are alternately arranged. Further, the permanent magnets 41 are disposed so as to face the inductor 30.

The magnet unit holder 50 is comprised of a boss portion 51 and a discoid portion 52. The boss portion 51 is coaxially arranged with the rotation axis X, and the discoid portion 52 connects with an end portion of the boss portion 51. Guide grooves 52 a, each extending in a radial direction of the rotation axis X, are formed at an outer circumferential portion of the discoid portion 52. When assembling the magnet unit 40 into the magnet unit holder 50, the arm portion 42 b of the yoke 42 of each magnet unit 40 is inserted into the corresponding guide groove 52 a. Further, a guide pin 53 projects from the discoid portion 52 on a line connecting each guide groove 52 a with the rotation axis X. When assembling the magnet unit 40 into the magnet unit holder 50, each guide pin 53 is inserted into an elongated guide hole 43 provided at the leg portion 42 c of the magnet unit 40. This configuration allows the magnet unit 40 to displace in the radial direction being guided and held by the magnet unit holder 50. Further, six slits, each extending from a center hole of the discoid portion 52 on the line connecting each guide groove 52 a with the rotation axis X, are formed.

A displacement mechanism 60, displacing the magnet unit 40 in the radial direction, is comprised of a direct-acting actuator 3 and a cylindrical operation body 62. The direct-acting actuator 3 serves as an operation driving source, and the operation body 62 is rotatably connected with a spool 3 a of the direct-acting actuator 3 via the bearing 61. The operation body 62 is inserted into the boss portion 51 of the magnet unit holder 50 through an inner circumferential surface of the discoid portion 52. Responding to axial linear displacement of the spool 3 a of the direct-acting actuator 3 via the bearing 61, the operation body 62 may slide along the inner circumferential surface of the discoid portion 52 in the axial direction. Six cam portions 62 a, each projecting in the axial direction and having an arm shape, are provided in the operation body 62. Each cam portion 62 a may insert into the slit 52 b of the discoid portion 52. An axial inclined surface 62 b is formed as a cam surface on an outer circumferential surface of the cam portion 62 a, and radial length of the inclined surface 62 b is continuously changed. A lower end portion of a leg portion 42 c of the magnet unit 40, serving as a cam follower, comes into contact with the inclined surface 62 a. Since the magnet unit 40 receives a large axial biasing force, which is caused by magnetic attractive force generated between the permanent magnet 41 and the inductor 30, the leg portion 42 c and the inclined surface 62 b of the cam portion 62 a constantly contact with each other.

The boss portion 51 of the magnet unit holder 50 is connected with a pulley 2, serving as a rotation driving means, and is rotatably supported by the bearing 4 mounted on an axial hole portion 12 a of the housing 12. The configuration allows the magnet unit holder 50 and the magnet unit 40 to rotate around the rotation axis X in conjunction with the rotation of the pulley 2.

When the magnet unit 40 rotates around the rotation axis X, the transmitting torque is generated by magnetic induction and then the inductor 30 rotates. In FIGS. 1 and 3, the direct-acting actuator 3 is controlled so that the spool 3 a of the direct-acting actuator 3 is pulled out until the stroke reaches the maximum extent. As a result, the leg portion 42 c of the magnet unit 40 is positioned at the lowest level of the inclined surface 62 b of the cam portion 62 a and the permanent magnet 41 is in the closest position to the inductor 30. Accordingly, the transmitting torque is maximized between the magnet unit 40 and the inductor 30. In other words, the rotational force of the impeller 20 is maximized, resulting in the maximum pump discharge capability.

On the other hand, in FIGS. 2 and 4, the direct-acting actuator 3 is controlled so that the spool 3 a of the direct-acting actuator 3 is pulled in until the stroke reaches the minimum extent. As a result, the leg portion 42 c of the magnet unit 40 is positioned at the highest level of the inclined surface 62 b of the cam portion 62 a, and the permanent magnet 41 is in the furthest position to the inductor 30. Further, the spaces between each permanent magnet 41 become larger. Accordingly, the transmitting torque is minimized between the magnet unit 40 and the inductor 30. In other words, the rotational force of the impeller 20 is minimized, resulting in the minimum pump discharge capability.

As described above, the pump discharge capability is changed from the maximum to the minimum by controlling the stroke of the spool 3 a of the direct-acting actuator 3. The direct-acting actuator 3 is controlled by a control signal from an engine ECU 90. The control signal, transmitted to the direct-acting actuator 3, is determined by an algorithm stored in the engine ECU 90 based on detection signals from non-shown sensors which respectively detect water temperature, throttle opening, and engine rotation speed.

For example, when the engine is under a large load, or when cooling function needs to be used for a high-temperature coolant and the like, the direct-acting actuator 3 is controlled so as to maximize the pump discharge capability. When the engine is under a low or a medium load, or when the temperature of the coolant is low, the direct-acting actuator 3 is controlled so as to lower the pump discharge capability and reduce an excessive coolant flow.

As just described, the engine ECU 90 outputs the control signal, which is determined based on the engine speed, the temperature of the coolant, and the throttle opening, to the direct-acting actuator 3 and adjusts the radial distance between the magnet unit 40 and the inductor 30 to conduct optimal control for limiting the coolant flow and the like to the minimum on a constant basis. When the engine is cold, the coolant flow is reduced to warm-up the engine in a short time period. Concurrently, unnecessary power is reduced for improvement of the fuel efficiency.

FIGS. 6 to 10 show a second embodiment in which the magnetic drive pump is employed as the water pump 100 of the engine. The water pump 100 is fixed to the engine block 1 by a fastening tool (not shown). The housing 12, the partition wall 13 defining the pump chamber 10 and the exterior chamber 11, and the pulley 2 serving as a rotation driving means are substantially the same as those used in the first embodiment. Further, the configuration of the impeller 20, the bearing 21, the supporting shaft 22, and the inductor 30 are substantially the same as those used in the first embodiment. The impeller 20, the bearing 21, and the supporting shaft 22 are disposed in the pump chamber 10 and the inductor 30 is fixed to the outer circumferential surface of the sleeve portion 20 a of the impeller 20.

As is apparent from FIG. 10, similarly to the first embodiment, each magnet unit 40 includes the segmental permanent magnet 41, and six permanent magnets 41 are used. However, compared to that of the first embodiment, a yoke 45 is different in shape. The yoke 45 is a segmental member having a lower surface which corresponds to an upper surface of the permanent magnet 41. Namely, a portion, corresponding to the magnet attaching portion 42 a of the first embodiment, comprises almost an entire portion of the yoke 45. A pin hole 45 a is formed at one side surface of both circumferential ends of the yoke 45.

The magnet unit holder 50 according to the second embodiment is similar to that of the first embodiment. The magnet unit holder 50 includes the boss portion 55 coaxially-arranged with the rotation axis X and the discoid portion 56 connected with the end portion of the boss portion 55. However, the shape is slightly different from that of the first embodiment. The boss portion 55 is connected with the pulley 2 and is rotatably supported by the bearing 4 fitted in the bearing hole 12 a of the housing 12. The dimension of the boss portion 55 is determined so as to be supported by the bearing 4. Further, through holes 55 a, penetrating through in the radial direction, are provided at two positions which are symmetric with respect to the axis. Further, a circular recessed portion is formed at the discoid portion 56 in a manner that a peripheral wall is left, and six pin holes 56 a are provided on an end surface of the peripheral wall. The six pin holes 56s are uniformly spaced away from each other in a circumferential direction. One end of a supporting pin (supporting shaft) 57 is inserted into the pin hole 56 a and the other end of the supporting pin 57 is inserted into the pin hole 45 a of the yoke 45. This configuration allows the discoid portion 56 to hold the magnet unit 40 so as to pivot in the radial direction.

The displacement mechanism 60 according to the second embodiment includes a cylindrical rotational operation body 65 which is rotatably connected to the spool 3 a of the direct-acting actuator 3, serving as an operation driving source, via the bearing 61. Responding to the axial displacement of the spool 3 a of the direct-acting actuator 3, which is linear motion, via the bearing 61, the rotational operation body 65 rotates while sliding in the axial direction along an inner circumference of the discoid portion 56. Another discoid portion 66 is formed at an end portion of the rotational operation body 65. A diameter of the discoid portion 66 nearly corresponds to an inner diameter of the circular recessed portion of the discoid portion 56 of the magnet unit holder 50. When the rotational operation body 65 is inserted into the boss portion 55 of the magnet unit holder 50 along an inner circumferential surface of the boss portion 55, the discoid portion 66 is fitted into the circular recessed portion of the discoid 56 of the magnet unit holder 50. Two inclined elongated-holes 65 a, extending obliquely relative to the axial direction, are formed at the rotational operation body 65, and each inclined elongated-hole 65 a is located so as to correspond to the through holes 55 a provided at the boss portion 55 of the magnet unit holder 50. When assembling the magnet unit holder 50 into the displacement mechanism 60, a free end of each guide pin 67, being press fitted into the through holes 55 a of the magnet unit holder 50, is insert into the corresponding inclined elongated-hole 65 a of the rotational operation body 65. This configuration allows the magnet unit holder 50 to rotate around the rotation axis X while being displaced in the axial direction by the direct-acting actuator 3.

Six link pins 68 project in the axial direction on an outer peripheral edge of the discoid portion 66 of the rotational operation body 65, and are uniformly spaced apart in a circumferential direction of the discoid portion 66. One end of an operation pin 69 is inserted into one of the two pin holes 45 a provided at the yoke 45 of the magnet unit 40, into which the supporting pin 57 is not inserted. The link pin 68 and the corresponding operation pin 69 are pivotally connected by a link body 70. Namely, a free end of the link pin 68 is inserted into one of link holes 70 a of the link body 70, and the operation pin 69 is inserted into the other link hole 70 a of the link body 70. This configuration allows the magnet unit 40 to pivot upwardly in the radial direction. Specifically, when the magnet unit holder 50 rotates in one direction, the link body 70 rises. Consequently, as shown in FIGS. 7 and 9, the magnet unit 40 pivots upwardly in the radial direction so as to be away from the inductor 30. On the other hand, as shown in FIGS. 6 and 8, when the magnet unit holder 50 rotates in the other direction, the link body 70 lies and the magnet unit 40 pivots downwardly in the radial direction so as to be close to the inductor 30.

Therefore, in the second embodiment, the pump discharge capability is changed from the maximum to the minimum by controlling the stroke of the spool 3 a of the direct-acting actuator 3.

In the above-described embodiments, the discharge mechanism 60 displaces the magnet unit 40 in the radial direction in order to change the radial distance between the magnet unit 40 and the inductor 30. However, the configuration, in which the displacement mechanism 60 displaces the inductor 30 in the radial direction to change the radial distance between the magnet unit 40 and the inductor 30, is not eliminated from the scope of the invention. Further, the segmental permanent magnet, i.e. a curved plate-shaped magnet, is used for the magnet unit 40. However, the magnets of other shapes may be employed. Furthermore, a magnetic field generating means, other than the permanent magnet, may be employed.

The invention is utilized as a magnetic drive pump which is applicable to various fields and changes the torque transmitted from a rotation source to the impeller by changing the radial distance between the magnet unit and the inductor.

In order to solve the above-described drawback, the magnetic drive pump includes the pump chamber 10, the partition wall 13 separating the pump chamber 10 from the exterior portion 11, the impeller 20 disposed in the pump chamber 10 and rotating around the rotation axis X, the inductor 30 unitarily rotating with the impeller 20 around the rotation axis X, the magnet unit 40 disposed at a position of the exterior portion 11 separated by the partition wall 13 where the magnet unit 40 faces the inductor 30 in the radial direction of the rotation axis X, the magnet unit 40 being rotatable around the rotation axis X, and the rotation driving means 2 driving the magnet unit 40 to rotate, wherein the displacement mechanism 60 is provided for changing the radial distance between the magnet unit 40 and the inductor 30.

According to the configuration, the radial distance between the magnet unit 40 and the inductor 30 is changed by the displacement mechanism 60, and the magnetic force acting on the inductor 30 is adjusted. Thus, in addition to changes of the rotation number by the pulley 2, the transmitting torque is adjusted to control the impeller rotation number by controlling the displacement mechanism 60. In case that this kind of pump is employed as a water pump for an engine, when the engine is cold and the temperature of the coolant is low, the distance between the magnet unit 40 and the inductor 30 is increased. Then, the impeller rotation number is lowered from a level defined by the linear relationship between the engine rotation number and the impeller rotation number, and the coolant flow is reduced. Thus, a time period for heating the coolant is reduced. Further, a load applied to the engine is reduced. Therefore, the improvement of the fuel efficiency is achieved.

The magnet driven pump is characterized in that the displacement mechanism 60 is formed as a cam displacement mechanism having an operation body 62 in which a cam portion 62 a displacing the magnet unit 40 in the radial direction is formed. The configuration allows the magnet unit 40 to move close to or move away from the inductor 30 in the radial direction of the rotation axis by changing the contact position between the operation body 62 and the leg portion 42 c. For example, the axial displacement may be readily changed to the radial displacement by employing the cam portion 62 a. Thus, the displacement mechanism 60 is incorporated in a limited and small space. Further, in the configuration, in case that the segmental permanent magnets 41, which are spaced away from each other in the circumferential direction around the inductor 30, respectively comprise the magnet unit 40, if at least one of the segmental magnet units 40 is moved away from the inductor 30 in the radial direction, the spaces between the magnet units 40 increase. In other words, once the displacement is manipulated, the magnet unit 40 is moved close to or moved away from the inductor 30, and each space between the magnet units 40 increases or decreases. Accordingly, the transmitting torque is effectively adjusted and the impeller rotation number is effectively reduced.

The magnet driven pump is characterized in that the magnet unit 40 is pivotable around a supporting shaft 57, which is provided at one circumferential end of the magnet unit 40 and is in parallel to the rotation axis X, and the displacement mechanism 60 is formed as a pivoting displacement mechanism which causes pivotal movement of the magnet unit 40 in the radial direction by manipulating the other circumferential end of the magnet unit 40 in the radial direction. According to the configuration, the magnet unit 40 is moved close to or moved away from the inductor 30 by being pivotally moved. Consequently, the transmitting torque is adjusted and the impeller rotation number is controlled. Since one end of the magnet unit 40 is displaced by manipulating the other end thereof in accordance with the principle of leverage, only small manipulation force is required and the displacement mechanism 60 is compactly configured.

According to the above-described embodiment, the pivoting displacement mechanism includes the rotational operation body 65 being rotatable around the rotation axis X and the link body 70 pivotably supported by the rotational operation body 65 at one end thereof and pivotably supported by the magnet unit 40 at the other end thereof. In the configuration, the rotational operation body 65 is rotated by the rotational displacement converted from the linear displacement of the spool 3 a or the rotational displacement input directly. Then, the link body 70 rises from a lying state. The postural change of the link body 70 allows the magnet unit 40 to pivot, and the one end of the magnet unit 40 is brought up. Thus, the magnetic force acting on the inductor 30 is reduced, and the impeller rotation number is reduced. Since the distance between the magnet unit 40 and the inductor 30 is adjusted by the pivotal displacement of the magnetic unit 40, the magnetic force acting on the inductor 30 may be subtly changed. Therefore, the impeller rotation number is readily adjusted to a desired level.

The principles, of the preferred embodiments and mode of operation of the present invention have been described in the foregoing specification. However, the invention, which is intended to be protected, is not to be construed as limited to the particular embodiment disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents that fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby. 

1. A magnetic drive pump comprising: a pump chamber; a partition wall separating the pump chamber from an exterior portion; an impeller disposed in the pump chamber and rotating around a rotation axis; an inductor unitarily rotating with the impeller around the rotation axis; a magnet unit disposed at a position of the exterior portion separated by the partition wall where the magnet unit faces the inductor in a radial direction of the rotation axis, the magnet unit being rotatable around the rotation axis; and a rotation driving means driving the magnet unit to rotate, wherein a displacement mechanism is provided for changing a radial distance between the magnet unit and the inductor.
 2. A magnetic drive pump according to claim 1, wherein the displacement mechanism is formed as a cam displacement mechanism having an operation body in which a cam portion displacing the magnet unit in the radial direction is formed.
 3. A magnetic drive pump according to claim 2, wherein the cam displacement mechanism is comprised of the operation body moving in an axial direction of the rotation axis and the magnet unit moving in the radial direction of the rotation axis.
 4. A magnetic drive pump according to claim 1, wherein the magnet unit is pivotable around a supporting shaft, which is provided at one circumferential end of the magnet unit and is in parallel to the rotation axis, and the displacement mechanism is formed as a pivoting displacement mechanism which causes pivotal movement of the magnet unit in the radial direction by manipulating the other circumferential end of the magnet unit in the radial direction.
 5. A magnetic drive pump according to claim 4, wherein the pivoting displacement mechanism includes a rotational operation body being rotatable around the rotation axis in response to rotational displacement and a link body pivotably supported by the rotational operation body at one end thereof and pivotably supported by the magnet unit at the other end thereof. 